Spring can help you to add realistic physic animation to your project file.
Create new file and draw elephant:)
Select frame 35
and Click F5
Create movie clips for tail and the element under tail.
Select bone tool
And connect this 2 movie clips
Please go to timeline
Click to first key frame and move tail to top
Click to last key frame and move tail to bottom
Select layer with animation and on property panel on the springs area click to enable.
Click on the bone and on spring area you can see Strength and Damping options
enter there 100
And after this you can compile and look to .swf file. So now your tail will move from top to bottom and in the end start moving from left to right, its look cool:) like dog want to eat:) I a little bit changed size of tail and now it bigger, it can help you see this effect.
Download Spring Source file.